succulent-identification-and-care

I've been very unsuccesful with the few succulents I have bought - not so sure what to do. This one (photos below) looks like it's shrivelling up. Pieces of it seem almost like they're rotting and are turning brown. I read that I should not water them often at all - what does that mean? How little is a little??

i have lots of these,do not be tempted to over water or under water.they will rot if you over water .a good mix of grit and Jonn innes will surfice and they like air and not draughts.a sunny shelf will do but not to be trapped in winter between the curtains.they are called I think lithops not sure of their type.